Flocculation and settling of liquid suspensions of finely-divided minerals



United States Patent FLOCCULATIGN AND SETTLING 01 LIQUID SUS- PENSIONS 0F FmELY-DIVIDED ll HNERALS Charles L. Ray, Wheaten, and Robert E. Batu-son, La

Grange, ill., assignors to Armour and Company, Chicage, 111., a corporation of Delaware No Drawing. Filed May 4, 1961, Ser. No. 197,635

8 Claims. (Cl. 210-53) This invention relates to the flocculation and settling of liquid suspensions of finely-divided minerals, and more particularly to tlocculating agents and processes by which coagulation and rapid settling of aqueous suspensions of finely-divided minerals are brought about, and the provision of filter aids for the same.

In the present practice involving the coagulation and settling of aqueous suspensions of finely-divided minerals, flocculating agents, such as guar gum, gelatin, carboxymethyl cellulose, and polyacrylamides, are employed. We have discovered that by mixing in said suspension a cationic flocculant, as hereinafter described, a synergistic effect is produced, bringing about very rapid settling and high clarity in a minimum of time and with a substantial saving in expense, and by employing a specific sequence in the adding of the flocculants to the suspension, a further beneficial elfect is produced.

A primary object, therefore, of the invention is to provide a process in which flocculating agents are combined with cationic liocculants for the elfective flocculation and settling of liquid suspensions of finely-divided minerals. A further object is to provide a process in which the fiocculants are added in sequence for improved flocculation and settling. Yet another object is to provide a combination of liocculants for producing better flocculation and settling of liquid suspensions of finelydivided minerals, while at the same time reducing the time and cost of the separating operation. Other specific objects and advantages will appear as the specification proceeds.

in one embodiment of the invention, a commercial flocculating agent, such guar gum, gelatin, carboxymethyl cellulose, polyacrylamide, etc, is added to an aqueous suspension of finely-divided minerals, such as, for example, a water and kaolin clay suspension, and to the suspension is added a cationic flocculant, such as an aliphatic substituted quaternary ammonium compound or mixtures thereof, or a water-soluble salt of N-aliphatic trimethylene diamine, N-aliphatic-N,N', I'-tris (hydroxyalkyl) trimethylene diamine, and after mixing is transferred to a settling tank to allow settling, the clarified water being then removed in the overflow andthe settled solids removed in the underflow. I

The aliphatic substituted quaternary ammonium compound may have the formula RrNX, wherein X is an acid-forming group and R is an aliphatic hydrocarbon group having from 1 22 carbon atoms, said compound being further characterized by the fact that at least one but not more than two of the Rs is an aliphatic hydro! carbon group having from 822 carbon atoms.

Specific examples of the aliphatic substituted quarternary ammonium compounds which can be employed are the dimethyl or diallyl dialkyl quarternary ammonium compounds, such as dimethyl distearyl quarternary amice monium chloride (Arquad 2HT) dimethyl dicoco quarternary ammonium chloride (Arquad 2C), dimethyl disoya quaternary ammonium chloride, dimethyl dioleyl quaternary ammonium chloride, and diallyl distearyl quaternary ammonium chloride, or the alkyl trimethyl quaternary ammonium compounds, such as trimethyl soya quaternary ammonium chloride (Arquad S), and trimethyl tallow quaternary ammonium chloride (Arquad T) or mixtures thereof, such as Arquad S-2C or Arquad T-ZC. For best results, we prefer to use Arquad 2HT or dimethyl dioleyl quaternary ammonium chloride.

Similarly, any N-aliphatic N,N',N'-tris (hydroxyalkyl) trimethylene diamine may be employed, but for best results we prefer to use N-tallow-N,N',N'-tris (Z-hydroxyethyl) -trimethylene diamine (Ethoduomeen T/1'3).

In preparing the cationic flocculants, including the quaternary ammonium compounds and aliphatic trimethylene diamines, we prefer to employ as starting materials amines derived from fatty acids having from 8-22 carbon atoms, and preferably from mixtures of fatty acids as found in coco, soya or tallow.

In test procedures, such as in the clarification of a suspension of kaolin clay, we found that when any of the commercial fiocculating agents, such as guar gum, carboxymethyl cellulose, and gelatin are employed, and where the cationic flocculants above described are separately employed, and the results recorded, the use of the cationic fiocculant with the first-mentioned commercial flocculants gives results in speed of clarification, degree of clarification, and amount of settling far in excess of the additive values of the two types of flocculants when used separately.

It was also found that when a polyacrylamide floccnlating agent is employed, and where the cationic flocculants above described are employed, the use of the.

Example I In order to observe the fiocculating, clarifying, and settling action in the minerals suspension system, 250 ml. graduated mixing cylinders were filled with the clay pulp and the fiocculant solution was added to the cylinder by means of a pipette. The cylinder was gently inverted several times after the flocculant addition to insure complete mixing. This was followed by immediate observation of the relative size of the floccule formed, the settling rate of the interface formed by the flocculated solids and the water phase, and the relative clarity of the supernatant water.

In the present Example I, the graduated cylinders were filled with a 3% solids clay pulp. Each of the referenced chemicals (cationic flocculants) was added tothe system at the rate of 12 /2 parts per million parts of pulp by weight. The cylinders were inverted gently five times, and

the relativefioc size, settling rate, and

supernatant clarity were determined.

: of flocculants. 1 was renbwesey several additional 1 'Scttling Rate, Milliliters/Minute 1 i V Flcculant(s) P.P.M. Relative Clarity "Relative Added 7 V Floc Size Untreated 4 12 V 24 36 44 60 7 96 Very cloudy. Control No. V 72 110 126 140 146 154 160 166 Clear Large Control N o. 5 64 V 96 108 140 1521 168 174 Control No 16 28 40 52 64 74 96 D Control No. 18 34 52 66 82 94 114 Gelatin 20 34 48 6O 76 86 4 112 Control No. 7 90 126 140 150 154 y 160 166 Control No. 118 134 148 162 Control No. 50 V 70 86 112 136 154 Control No. 7+Gelatin, 50 66 82 96 110 126 146 CMCwas added to the system. This was followed by 0 followed by several additional inversions of the cylinder- Example II V inversions of the cylinder to assure complete-mixing, and r The testing procedure was as in Example I.' The gradobservation of the clarity and settling rate.

a r r Milliliters s ttled/Minute i l Floeculanfls) P.P.M. V Relative Relative 1 i V V Clarity Floc Size Separan N1 20 6% l 96 142 156 164 16s 2172 178 180 Almost clear Large. Separan NP20 and Control 4% and 1V 90 138 152V 160 164 168 178 do n Do. 4' V v V V v V 1 Untreated 4 10 V 14 20 7 24 3O 4O 52 Very c1ondy. Clear. 7

uated cylinders were filled with a 3% clay pulp. The Example- 'IV A further. test was made similar to the procedure'of Example I except that guar gum"(Guartec) was used in place of the gelatin and was foundtto increase the settling rate of the suspended solids and to improve the clarity of to insure complete mixing. One test was conducted in U which only CMC at the rate of 3% parts 'per million was added. These results may be compared to those inExthe supernatant Water. It was found that up, to 50% of the Guartec that is required to provide a moderate settling rateand moderate clarity may be replaced with thejreferenced chemicals (cationic flocculants) to provide a syner- V gistic settling rate and improvedclarity, .IThe graduated cylinders were filled with a 5.. clay pulp. in the first test,

lamps 4 guar gum (Guartec) was added to the system at therrate Mililiters Settled/Unit of Time (Min) v l I Control No. Plus Relative Clarity Relative 1 CMO- V Floc Size 1 1% 2 2% 3 4 a 5 Untreated 4 12 24 36 44 60 76 96 'Very cloudy '4, V 122 170 180 186 190 192 196 5 90 130 158 172 178 182 190 '6 50 90' 130 152 166 172- 182 7 80 140 164 172 ;180 184 190 CMC alone 42 64 86 104 120 132 152 tothe system at the'rate of approximately 4% parts per million parts of pulp by weight followed by inverting the of 6% parts per million parts of pulp by weight, followed by inverting the cylinderseveral times and observation of.

' the clarity and the settling rate. In the remaining tests,

the Guartec was added at the rate of-4% or 3% parts per million parts of pulp, and'the'cylinders were inverted several times. This .was. immediately followed addition of the referenced chemicals at arate suflicient tomake a total'of 6% parts offlocculant per million parts of-pulp.

The cylinders were again inverted several times to assure; a

complete mixing, and theclarity 'and'settling rates were cylinder several times. Dimethyl dialkyl ammonium chlo- V 1 observed. I

Reference Chemicals Mummers Settled/Minute I f V. I I Relative, Relative P.P.M. Guartee 'Glarity Floe sizefl 4 Control; VP.P.M. 1 r x N0. 1 1- 1% 2. (2% '3' I '41 51 'Untreated s s 14 18' 24 2s 40 l 5 0 Veryeloudy I -6% 124 54 7 7s 98V 116 12s 1427 154 Sligl1tly'eloudy ed m. 4% 4 1%v as 72 Y 100 "124- 1138' 146 "156 162 Large." 3% a 4 3% 36 74 104 128 140 148 156 162 d 1 Do.

ride was added at the rate oiapproxiinately 1 /2 parts per 4 Example V millionparts of pulp by weight. for a total of 6% parts The testing procedure'was as inlExample' I, except that.

a total of 9 parts of fiocculant per million parts of pulp was added to the system.

The time interval was recorded from the point of addition of the treated pulp to the filter until the last trace Reference Chemicals Milliliters Settled/Minute Relative Relative P.P.M. Guartec Clarity Floc Size Control N o. P.P.M. 1 1% 2 2% 3 4 5 q 32 66 96 118 134 142 154 160 Slightly cloudy--. Large. 6% 4 2% 54 110 134 146 152 158 164 168 Almost clear Do. 41 4 4% 62 I22 140 150 156 160 166 170 Clear Do.

Example VI of free water on the filter cake disappeared.

In the following test, finely-divided coal was mixed with kaolin clay in a 1:1 ratio by weight and pulped in water to 5% total solids. The testing procedure was as in Example I. The graduated cylinders were filled with coal-clay pulp. In the first example, a guar gum (Guartec F) was added to the system as the sole fiocculant at a rate of 12 /2 parts per million parts of pulp, followed by inverting the cylinder several times and observation of the clarity and the settling rate. In the second example, a guar gum (Guartec F) was added to the system at a rate of 6 /2 parts per million parts of pulp, followed by inverting the cylinder several times. The diacetate salt of N- tallow trimethylene diamine was next added to the system at a rate of 6% parts per million parts of pulp, followed by several additional inversions of the cylinder to assure complete mixing and observation of the clarity and settling rate. r

Seconds of Filtering To Obtain Moist Filter Cake Flocculant(s) Used P.P.M.

Blank (Untreated) Control No. 4 332 CMC and Control N 303 GMC 461 Guartec and Control No 4. 263

5 {Parts Flocculated per Settling Rate-Milliliters/Min.

5," Million Parts of Pulp Relative Relative Clarity Floc Size Gnartec F Reference 1 1% 2 2% 3 4 5 Chemical 12 46 90 124 143 153 160 170 176 Cloudy Medium.

634 6% 96 142 156 162 168 172 178 181 Clear Large.

Untreated 2 6 8 18 24 3O 42 54 Cloudy Example VII In this test, a copper ore was ground to minus 200 mesh size and pulped in water to a solids content of 5% by weight. The graduated cylinders were filled with the copper slirnes pulp, and the exact test procedure, flocculating agents, and flocculating agent addition rates as outlined in Example VI were followed.

Parts Flocculant Per Million Part s Pulp Settling Rate-Milliliters/Minute Relative Clarity GuartecF i Reference 1 1% 2 2% 3 4 5 Chemical 12y i 126 174 186 194 196 200 204 207 Slightly cloudy, 6 6, 4 168 186 195 198 202 204 206 209 Clear. Untreated 4 30 G6 88 104 140 172 Cloudy.

Example VIII In the following test, it was found that the combination of the referenced chemicals (cationic flocculants) with guar gum or carboxymethyl cellulose resulted in a reduction of filtering time even further than when these flocculants are used alone at an equivalent addition rate.

In the tests, a 500 ml. graduated cylinder was filled with the cationic flocculant and goat gum are admixed prior to application, a reaction of sorts may occur as evidenced by increased turbidity in the flocculant make-up solution. While the nature of this desired reaction of sorts between the cationic flocculant and other commercial fiocculants, such as guar, is not fully understood, it is believed that this reaction is at least in part responsible for the cationic intensification of the initial flocculation provided by such commercial flocculants. When the flocculants are added separately, with the cationic flocculant being added in the second stage, a more effective flocculation is accomplished.

In a test procedure with a coal-clay system, the synergistic effect between the cationic fiocculant (referenced chemicals) and guar gum was evidenced when comparing settling rates between the use of the cationic flocculants used alone, the guar gum us ed alone, and the combine:

tions of, the cationics'with guar'gum, v p 2 While in the foregoing specification we have set forth 3 in considerable detail an embodiment of the invention 7 suspension a cationic flocculant selected from the group consisting'of a quaternary ammonium compound totally substituted with aliphatic radicals, at least one of which is a long chain hydrocarbon radical, and a Water-soluble 1 presence of at least one and no morethan two aliphatic hydrocarbon radicals having 13-22 carbon. atoms. 7

3. The process of claim 2 in which the quaternary ammonium compound is dimethyl dicoco ammonium a.

chloride. 7 V I v 4. The process of claim 2 in which the quaternary ammonium compound is tallow trimethyl ammonium chloride.

8 2 5. The process of claim 2 in which the fiuocculant first mixed into the' suspensio'n comprises guar gum.

,6. A process for fiocculating and settling finely-divided minerals in liquid suspensioncjomprising the steps of first mixing into said suspension a'flo'cculant selected from the group consisting of a polyacrylamide, carhoxymethyl cellulose, guar gum and gelatin, and then mixing into said suspension a water-soluble salt of N-aliphatic trimethylene 7 '7 diamine.

'7. The process of claim 6 in which the diamine is N- tallow-N,N,N-tris (Z-hydroxyethyl)-trimethylene diamine.

e 8. The process of claim 6 in which the fiocculant first mixed into the suspension comprises guar gum. 7

References Cited in the file of this patent f V 'UNITED STATES PATENTS 2,315,734 Rals ton et al Apr. 6, 1943 r 2,509,261 Carosella May 30, 1950 2,862,880 Clemens Dec. 2', 1958 2,937,143 'Goren May 17, 1960' 2,970,158 Levis -4 Jan. 31, 1961 3,020,231 Colwell er al. Feb. 6, 1962 3,055,827 .Wi1ey' Sept. 25, 1962 I i x FOREIGN PATENTS j "551,627 1 Canada Jan. 14, 1958 528,842 I Belgium 1 May 31, 1954 589,543 Canada Dec. 22 1 959 a V OTHER REFERENCES Surface Active Agents and Detergents, vol. II by SchwartzetaL, Interscierice Publishers, 'Inc., New York (1958), pp. 114 and 217. r 2

Industrial & Engineering Chemistry. (periodical), vol. 46, November 7, pages 1485 to' 1490: (July 1954). 

1. A PROCESS FOR FLOCCULATING AND SETTLING FINELY-DIVIDED MINERALS IN LIQUID SUSPENSION COMPRISING THE STEPS OF FIRST MIXING INTO SAID SUSPENSION A FLOCCULANT SELECTED FROM THE GROUP CONSISTING OF A POLYACRYLAMIDE, CARBOXYMETHYL CELLULOSE, GUAR GUM AND GELATIN AND THEN MIXING INTO SAID SUSPENSION A CATIONIC FLOCCULANT SELECTED FROM THE GROUP CONSISTING OF A QUATERNARY AMMONIUM COMPOUNG TOTALLY SUBSTITUTED WITH ALIPHATIC RADICALS, AT LEAST ONE OF WHICH IS A LING CHAIN HYDROCARBON RADICAL, AND A WATER-SOLUBLE SALT OF N-ALIPHATIC TRIMETHYLENE DIAMINE. 